Wafer processing apparatus having dust proof function

ABSTRACT

The wafer processing apparatus includes a chamber that is pressurized to a pressure that is higher than the pressure of the exterior thereof, an opening portion through which the interior and the exterior of the chamber are in communication with each other, and a door that closes the opening portion. When the opening portion is closed by the door, a portion of the opening remains as an aperture uncovered by the door. In conventional semiconductor wafer processing apparatus, the interior of the apparatus is sealed and pressurized in order to keep a high degree of cleanness in the wafer processing portion, and therefore airflow is generated due to a pressure difference between the interior and the exterior of the apparatus. With the above feature of the invention, it is possible to suppress creation of such airflow and prevent dust from entering the wafer processing apparatus to eliminate wafer contamination.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a Continuation-in-Part of application Ser.No. 10/330,092, which was filed on Dec. 30, 2002, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wafer processing apparatus havingdust proof function used in manufacturing processes for semiconductordevices, electronic parts and related products, or optical disks etc.The dust proof function is a function to prevent dust that is generateddue to an opening/closing operation of an opening portion of theprocessing apparatus from entering the interior of the processingapparatus, when a semiconductor wafer (which will be simply referred toas wafer hereinafter) is transferred from a clean box for storing wafersinto the processing apparatus through the opening portion of theprocessing apparatus for processing.

2. Related Background Art

Manufacturing of wafers, which are used for semiconductor devices etc.,must be performed under a condition in which a high degree of cleannessis ensured. Therefore, the manufacturing of wafers was generallyperformed in a clean room the whole interior of which is kept in ahighly clean condition. However construction and maintenance of a largeclean room with a high degree of cleanness require a significant initialinvestment and service costs. In addition, even if once a plantinvestment is made for such a clean room, a modification of the layoutof the room might be required later due to a modification in themanufacturing process, which would require a large additionalinvestment. Therefore, use of clean rooms is uneconomical. In view ofthe above-described situation, recently a certain method has been widelyadopted, that is, to keep a high degree of cleanness not within thewhole interior space of a room but only within a small environmentalspace (which will be referred to as a mini-environment) inside aprocessing apparatus to attain the effects same as those obtained bykeeping a high degree of cleanness within the whole of the room. (In thefollowing, a processing apparatus that adopts this method will be calleda clean apparatus.)

Specifically, in that method, clean apparatus are set in a manufacturingroom with a certain layout, and wafers are transferred from one cleanapparatus to another within a wafer storage container (which will bereferred to as a clean box hereinafter) whose interior is kept in ahighly clean condition. The clean box is attached to a predeterminedopening provided on a clean apparatus in such a way as to prevent dustfrom entering from the exterior, and the wafers are brought into and outof the clean apparatus through that opening. Thus, the space to whichthe wafers are exposed can be always kept highly clean without a needfor establishing a highly clean condition within the whole interior ofthe manufacturing room. Therefore, this method realizes the effects sameas those attained by establishing a clean room condition within thewhole of the room, and so it is possible to reduce construction andmaintenance costs to realize an effective manufacturing process.

In the above-described clean apparatus, in order for themini-environment to be kept in a highly clean condition, the pressurewithin the mini environmental portion is arranged to a pressure(P_(a)+ΔP) that is higher than the external ambient pressure(represented here as P_(a), which is generally the atmospheric pressure)by a predetermined pressure difference (ΔP). This creates an overallairflow from the interior of the mini-environment to the exteriorthereof, so that dust would be exhausted to the exterior. In addition,airflow from the exterior can be prevented from entering themini-environment, which prevents dust in the exterior from entering themini-environment.

Conventionally, the general understanding has been that if themini-environment is sealed as tight as possible, it is possible toprevent external dust from entering and to establish a high degree ofcleanness. Therefore, the mini-environment is isolated from the externalenvironment and placed in a completely sealed state by a door thatcloses the opening provided on the mini-environment except when themini-environment is connected with the clean box for transferring of thewafer.

In the conventional apparatus as described above, since themini-environment is isolated from the exterior or the ambient except forduring the transfer of a wafer, the wafer in the interior is kept in ahighly cleans condition. However, when the door is opened fortransferring of the wafer, airflow from the interior of themini-environment to the exterior is created due to the above-describedpressure difference ΔP between the interior and the exterior of themini-environment, which causes the following problem.

As described above, as long as an additional pressure is applied to theinterior of the mini-environment, the airflow is inevitably created whenthe door is opened. In the conventional apparatus, the pressuredifference ΔP is especially large at the moment when the door is opened.Therefore, the flow rate of the airflow created at the moment of openingthe door is larger than the flow rate created by a pressure differenceΔP after elapse of a certain time. In addition, the airflow generated atthe moment of opening the door involves significant turbulence.

On the other hand, the pressure in a clean box is substantially equal tothe atmospheric pressure, and therefore, when airflow involvingturbulence is generated at the opening, the airflow will be drawn intothe interior of the clean box. The airflow flowing out of the openinggenerally includes dust to be exhausted from the interior of themini-environment. In addition, dust in the exterior is also stirred upby the airflow. Therefore, the airflow drawn into the clean box includesdust, which will contaminate the wafers inside the clean box todeteriorate the quality of the wafers.

SUMMARY OF THE INVENTION

An object of the present invention is to reduce creation of theabove-described airflow involving turbulence at the opening to provide awafer processing apparatus in which such airflow is not drawn into theinterior of a clean box.

Another object of the invention is to suppress creation of theabove-mentioned airflow to prevent contamination of wafers by providinga wafer processing apparatus comprising, a chamber that is pressurizedto a pressure that is higher than the pressure of the exterior thereof,an first opening portion through which the interior and the exterior ofthe chamber are in communication with each other, and a door that closessaid first opening portion, wherein when the first opening portion isclosed by the door, an aperture through which the interior and theexterior of the chamber are in communication with each other remains.Specifically, the invention provides a wafer processing apparatus inwhich an aperture through which the interior and the exterior of thechamber are in communication with each other is present on or in thevicinity of the door under the state in which the first opening portionis closed by the door. The aperture that is present under the state inwhich the first opening portion is closed by the door may typically be achink formed around the door or a second opening formed on the door, aswill be described in connection with the embodiments of the presentinvention.

A still other object of the present invention is to provide a waferprocessing apparatus in which a protruding wall is provided in thecircumference of the opening and along the edge of the opening. Withthis aspect of the invention, it is possible to prevent dust that isstirred up by the above-mentioned airflow from entering the clean boxand to enhance effects of preventing wafer contamination.

Other objects and aspects of the invention will become apparent from thefollowing description of embodiments with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall view showing a wafer processing apparatus to whichthe present invention is applied.

FIG. 2 is a drawing showing a portion including an opening of asemiconductor processing apparatus according to the first embodiment.

FIG. 3 is a drawing schematically showing a cross section of theapparatus of the first embodiment under the state in which an opening ofa mini-environment portion is closed by a door.

FIG. 4 is a drawing schematically showing a cross section of theapparatus of the first embodiment under the state when the door of theopening of the mini-environment portion is made open.

FIG. 5 is a perspective view showing a portion of the apparatus of thefirst embodiment, which is provided with a protruding wall having aneaves.

FIG. 6 is a drawing schematically showing a chink defined by a door anda wall of the mini-environment portion according to the secondembodiment under the state in which the opening of the mini-environmentportion is closed by the door.

FIG. 7 is a drawing showing a second opening in a semiconductor waferprocessing apparatus according to the third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

In the following an embodiment of the present invention will bedescribed with reference to annexed drawings. FIG. 1 is a drawingshowing the overall structure of a semiconductor wafer processingapparatus 10. The semiconductor wafer processing apparatus includes amini-environment portion 5, in which a robot arm 11 is provided. Theinterior of the mini-environment portion 5 is pressurized to a pressurethat is higher than the ambient pressure (that is generally, theatmospheric pressure) outside the semiconductor wafer processingapparatus 10.

The mini-environment portion 5 has a window opening 2 through which therobot arm 11 receives wafers 7. FIG. 2 is a drawing showing the windowopening 2 as seen from the interior of the mini environment portion 5(that is, as seen in the direction indicated by arrow X in FIG. 1). Thewindow opening 2 is closed by a door 3 as shown in FIG. 2, when thetransferring of wafers 7 is not performed. Upon opening the windowopening 2, the door 3 is swung about a pivot that is provided in thevicinity of a driving portion to shift to a position shown by the dashedline in FIG. 1. At that position, the door 3 is spaced apart from theopening and in an inclined state. Then, the door 3 is moved downwardfrom the position shown by the dashed line. In connection with this, thedoor 3 is adapted to be driven by the driving portion to move up anddown (in the up-and-down direction in FIG. 1). When the window opening 2is to be closed by the door 3, the door 3 is moved following asequential process that is reverse to the above-described process.

A clean box 6 is used for transferring wafers 7 from one waferprocessing apparatus 10 to another. The wafers 7 are accommodated in theclean box 6, which is closed by a clean box door 4 in a highly airtightmanner. Thus, when the wafers 7 are accommodated in the clean box 6, theinterior of the clean box 7 is ensured to be in a highly cleancondition. The interior of the clean box may be filled with a gas suchas nitrogen of high purity.

The semiconductor processing apparatus 10 is provided with a dockingplate 12 on which the clean box is to be placed. The docking plate 12 ismovable in the horizontal direction in FIG. 1 or FIG. 3, along a railprovided below it. The docking plate is driven by a driving mechanism(e.g. an air cylinder), which is not shown in the drawings, so that thedocking plate can move toward and away from the mini-environment portion5. When the clean box 6 is placed on the docking plate 12 and movedtoward the mini-environment portion 5, the vertical position (in thevertical direction of the window opening 2) and the horizontal position(in the horizontal direction of the window opening 2) of the clean boxare adjusted in such a way that the clean box door 4 is fitted to thewindow opening 2. At that time, the clean box 6 that has been broughtcloser the mini-environment portion 5 is not in contact with themini-environment portion 5, but the docking plate 12 is arranged to bestopped at a stop position at which a clearance 14 is formed between theclean box 6 and the mini-environment portion 5. The clearance 14 isformed between the peripheral end portion of the clean box 6 facing thewindow opening 2 and the outer wall of the mini-environment portion 5.The clearance is about 2 mm.

As shown in FIG. 2, the sizes of the door 3 and the window opening 2 aredesigned in such a way that when the window opening 2 is closed by thedoor 3, apertures or chinks 1 remain between the wall near windowopening 2 and the door 3 as seen from the interior of themini-environment portion. It should be noted that in FIG. 2 the chinks 1are illustrated in an exaggerated manner in order to facilitatevisualization thereof. A preferable form of the chinks 1 in thisembodiment will be described later.

It is preferable that the chinks 1 are uniformly formed around the door3 in the closed state so as not to trouble air flow from the interior ofmini-environment portion 5 to the exterior thereof to create an air flowinvolved into inner space of a clean box 6. However, if the chinks 1 areformed around the door 3 in the closed state, it is necessary forproviding means for determining whether the door is stopped or not at apredetermined position of closing the window opening 2, foracknowledging an appropriate stop position, or the like. As for suchmeans, it may be considered for example to provide a system forcontrolling the stop position onto a driving system (not shown) fordriving the door 3. On the other hand, the system provided on thedriving system may not easily recognize the appropriate stop position ormay make the system complicated, and therefore, such system is notproper countermeasure.

In consideration of the above, in the present invention, projections 3 aare formed at respective four corners of the door 3 so as to berespectively in contact with periphery of the outer wall ofmini-environment portion 5 around the window opening 2 so that the stopposition of the door 3 is controlled. This countermeasure slightlyreduces an effect obtained by the chinks 1, but can simply and easilycontrol the stop position of the door 3. In addition, it is consideredthat above described position of projections 3 a is farthest from theopening of the clean box 6 or wafers housed within the clean box 6, andtherefore turbulent air flows caused by the projections 3 a have leastinfluence on interior of the clean box 6. Furthermore, by forming theshape of the projection appropriately, it is possible to reduce theturbulence of air flow.

As described above, the positions of projections 3 a are designed inconsideration that the influence of the turbulent air flows upon theclean box should be minimum. However, if the condition of the clean box6, mini-environment portion 5 or the like is, for example arranged suchthat a factor such as the pressure difference between the interior andthe exterior of the mini-environment portion 5 reduces the influence ofthe turbulent air flows, the number of projections can be varied orlocations of the projections can be changed to more proper position onthe apparatus.

In addition, in the present invention, the apparatus is designed suchthat an end part at the window opening 2 side of the clean box 6 is setso as not to be in contact with the outside surface of themini-environment portion 5, but so as to make the clearance 14.Furthermore, the clearance 14 is formed to close to the chinks 1. Sucharrangement prevents the air flow from the interior to the exterior ofthe mini-environment portion 5, from rapidly changing the flowdirection. In case that the air flow carries dust, if the flow directionrapidly changes, the dust is thrown off the flow and may be reached intothe inner space of the clean box 6. By preventing the rapid directionchange of the gas flow, the possibility that the dust carried by the airflow is reached into the inner space of the clean box 6 is remarkablyreduced. In addition, the arrangement in which the clean box 6 is not incontact with the mini-environment portion 5 provides further effect ofpreventing the dust creation caused by the contact therebetween. Here, adescription will be made of a non-transferring state during which thetransferring of the wafers 7 is not performed. This state includes astand-by state (during which the processing of a wafer 7 is notperformed) and a state during which the processing of a wafer 7 isperformed. In this state, the opening is being closed by the door 3 asshown in FIGS. 2 and 3. In this state, air is flowing constantly fromthe interior of the mini-environment portion 5 that is adapted to have apressure higher than the ambient pressure to the exterior thereofthrough the chinks 1 as an aperture which still remains after closingdoor 3. Therefore, the pressure difference between the interior and theexterior created by the pressurization becomes small in the vicinity ofthe door 3.

Next, a description will be made of a state during which thetransferring of a wafer 7 from a clean box 6 is performed. This stateincludes a state during which a wafer 7 is brought into (or loaded to)the mini-environment portion 5 upon starting of the wafer processing anda state during which a wafer 7 is taken out of (or unloaded from) themini-environment portion 5 upon completion of the wafer processing.After the preceding process by another processing apparatus has beencompleted, the clean box 6 is transferred from that processing apparatusand placed on the docking plate 12. The clean box 6 placed on thedocking plate 12 is moved with a movement of the docking plate 12 to aposition at which the clean box door 4 is close to the door 3 of themini-environment portion 5 toward the window opening 2. When a surfaceof a member 22 of a first stopper abuts a surface of a second stopper21, the docking plate 12 cannot move any more, namely it is stopped.After the movement of the docking plate 12. is stopped, the clean boxdoor 4 is held by the door 3 by means of vacuum suction or other means,and the door 3 is opened together with the clean box door 4, so that thewindow opening 2 is made open as shown in FIG. 4. As described above,since the pressure difference between the interior and the exterior ofthe mini-environment portion 5 is small even in the state in which thewindow opening 2 is closed by the door 3, the door 3 can be openedeasily without a significant resisting force caused by the pressuredifference. In addition, airflow from the interior to the exterior ofthe mini-environment portion 5 created when the door 3 is opened issmall. Therefore, contrary to conventional apparatus, airflow involvingdust is not drawn into the clean box, and it is possible to prevent dustexisting in the exterior of the mini-environment portion 5 and in thevicinity of the opening from being stirred up due to the creation of theairflow. Consequently, it is also possible to prevent dust from enteringthe clean box 6. Since the clean box 6 and the mini-environment portion5 are not in contact with each other, the airflow that is created as thedoor 3 is opened does not enter the clean box 6 but flows to theexterior through window opening 2 and the clearance 14.

After that, the door 3 is moved downward by the driving portion togetherwith the clean box door 4 held by it, and a wafer 7 is picked up andbrought into the mini-environment portion 5 by the robot arm 11. Afterthe wafer 7 is set at a prescribed position in the mini-environmentportion 5, the door 3 is moved upward by the driving portion to closethe window opening 2 by causing the projections 3 a to contact withperiphery of the window opening 2.

In the arrangement of the present invention, gap of the chinks 1 and theclearance 14 (and pressure in the mini-environment 5) are set such thata flow rate or volume of gas (air in the present embodiment) which flowsfrom the interior to the exterior of the mini-environment portion 5through the chinks 1 in the state in which the door 3 closes the windowopening 2, is substantially equal to a flow rate of gas which flowsthrough a gas flow path which is formed between the clean box 6 and themini-environment portion 5 when the wafer 7 is transferred from or intothe inner space of the clean box 6. As the result, irrespective of thestate of the door 3, a certain flow rate of the gas flowing from theinterior to the exterior of the mini-environment portion 5 is assuredconstantly. Hence, even if the door 3 moves to the opening state, rapidchange of the gas flow rate can be prevented, and no gas flows into theinner space of the clean box 6 when the gas flows from window opening 2to the exterior space through the clearance 14. Therefore, if there isdust within the mini-environment portion 5, that dust is carried by thegas flow to the exterior space, but not to be reached into the innerspace of the clean box 6.

The width of the chinks 1 may be appropriately optimized in relation tothe interior pressure. In this embodiment, the interior of themini-environment is so pressurized that the interior pressure is higherthan the exterior pressure (i.e. the atmospheric pressure) by 2 Pa (atypical value). Under this condition, the width of the chinks 1 is set,for example to 2 mm (a typical value). Then, each of the upper and lowerchinks 1 a shown in FIG. 2 will have an area of about 315 mm×2 mm, andeach of the side chinks 1 b shown in FIG. 2 will have an area of about290 mm×2 mm. By providing chinks having such areas, it is possible toeffectively prevent dust in the exterior from entering the interior andto prevent creation of airflow including dust due to a pressuredifference between the interior and the exterior of the mini-environmentportion 5. This is an advantageous effect of the present invention.

In addition to the reduction of the creation of airflow involving dustattained by the chinks 1, contamination of the wafers 7 can be furtherreduced by proving a protruding wall 8 disposed on the outer surface ofthe mini-environment and in the circumference of the window opening 2 asshown in FIG. 5. The protruding wall 8 may comprise, for example, aplate-like member provided at the circumference of the window opening 2along its edge, extending substantially perpendicular to the wall of themini-environment portion 5. The thickness of the protruding wall 8 wouldbe designed in such a way that the protruding wall 8 has a certaindegree of strength with which its shape will be preserved even ifsomething collides against it. On the other hand, the height of theprotruding wall 8 would be so designed as to prevent dust from enteringthe clean box with airflow. In this embodiment, the height of theprotruding wall is 22 mm (a typical value).

If the apparatus is provided with the protruding wall 8 having theabove-mentioned height, even when dust existing in the exterior of themini environment portion 5 and in the vicinity of the window opening 2is starred up by airflow, the protruding wall 8 would block or preventthe dust from entering the clean box 6.

Furthermore, the advantageous effects of the protruding wall 8 can beenhanced by providing an eaves 9 on the protruding wall 8 as shown inFIG. 5. The eaves 9 may comprise, for example, a plate-like member thatis provided on the top or the protruding wall (i.e. the end of theportion of the protruding wall opposite to the wall of themini-environment) and extending inwardly toward the opening. The lengthof the inward extension may be appropriately determined in such a waythat it would not interfere with the flange portion of the clean box,when the flange portion is connected to the window opening 2. Generally,the larger the width of the eaves is, the more effectively it canprevent dust from entering the clean box. However, on the other hand, alarge eaves width would deteriorate accessibility in connecting theclean box to the opening. For example, in this embodiment, the width ofthe eaves is designed to be 2 mm (a typical value).

As described above, additional advantageous effects are realized, inaddition to the advantageous effects of the chinks 1, by providing theprotruding wall 8 with or without the eaves 9.

In order to realize the advantageous effects, the protruding wall 8 isnot necessarily required to be provided in combination with the chinks1. Even when only the protruding wall 8 is provided without theprovision of the chinks 1, the advantageous effect of preventingexternal dust from entering the interior of the mini-environment or theclean box can be realized.

Embodiment 2

In the above-described first embodiment, the chinks 1 are formed aspartial areas of the window opening 2 that remain uncovered by the door3 when the door 3 is in contact with the wall of the mini-environmentportion 5. However, the form of the chink 1 is not limited to that. Asshown in FIG. 6, the chink 1 may also be formed, for example, as a chinkor clearance that is formed between the door 3 and the wall of themini-environment portion 5 under a state in which the door 3 ispositioned, for covering the window opening 2, in such way that any partof the door 3 is not in contact with the wall of the mini-environmentportion 5. As will be understood from the above, the advantageouseffects similar to the effects of the first embodiment can be realizedas long as the chink has an size that does not easily allow entrance ofexternal dust and can reduce the pressure difference between theinterior and the exterior of the mini-environment 5.

Like in the first embodiment, the effect of preventing the entrance ofdust can be improved also in this second embodiment by providing aprotruding wall 8 with or without an eaves 9.

Embodiment 3

In the above-described second embodiment, the chink 1 is defined betweenthe door 3 and the window opening 2. However, as shown in FIG. 7, secondopenings (or apertures) 13 may be provided on the door 3. For example,the second openings 13 are provided at peripheral portions on the door3, while the door is configured to completely cover the window opening 2(shown by the broken line in FIG. 7) when it is in the position forcovering the opening. In this case also, the interior of the apparatusis in communication with the exterior through the second opening on thedoor 3. Therefore, the pressure difference between the interior and theexterior is reduced and advantageous effects similar to those in thefirst or second embodiment can be realized.

Like in the first embodiment, the effect of preventing the entrance ofdust can be improved also in this third embodiment by providing aprotruding wall 8 with or without an eaves 9.

While in the first to third embodiments, an opening(s), such as thechinks 1, that has an elongated shape is adopted, the present inventionis not limited to such an elongated shape of the opening in realizingthe advantageous effects. However, as is the case with theabove-described first to third embodiments, the openings that arearranged uniformly in the vicinities of the four sides of the door areadvantageous and preferable in reducing the pressure gradient on theplane of the door. Therefore, a set of the chinks 1 is the mosteffective form.

The present invention realizes the following advantageous effects.

(1) In semiconductor wafer processing apparatus, with the provision ofan aperture under the state in which an opening for allowing transfer ofwafers into the mini-environment portion serving as a wafer processingportion is closed by a door, it is possible to reduce creation ofairflow to prevent contamination of wafers with dust.

(2) With the provision of an protruding wall with or without an eavesalong the edge of the opening, it is possible to prevent wafers frombeing contaminated by dust that is stirred up by airflow created whenthe door is opened.

While the described embodiment represents the preferred form the presentinvention, it is to be understood that modifications will occur to thoseskilled in that art without departing from the spirit of the invention.The scope of the invention is therefore to be determined solely by theappended claims.

1. A wafer processing apparatus for processing a wafer transferred froma clean box having an access opening to allow accessing an inside of theclean box and a lid to close the access opening wherein the inside ofthe clean box is separated from a circumstance of the outside of theclean box by closing the access opening with the lid, said waferprocessing apparatus comprising: a chamber pressurized to a pressurehigher than a pressure of an outside of the chamber; a first openingformed on a part of a wall of the chamber for transferring a waferbetween the clean box and the chamber through said first opening; and adoor member capable of holding the lid of the clean box, wherein saiddoor member moves between a closed position to close the access openingand said first opening and an open position to open the access openingand said first opening; wherein an outer periphery of said door memberis larger than an outer periphery of said first opening to cover a wholepart of said first opening from the inside of said chamber, wherein afirst gap is formed between the wall of the chamber and an outerperiphery portion of said door member which portion is larger than theouter periphery of said first opening at the closed position, wherein astopping device is provided to stop the clean box a predetermineddistance away from the outer surface of the wall to thereby form asecond gap between the clean box and an outer surface of the wall of thechamber, wherein a flow rate of gas flowing through the first gap froman inside of the chamber to an outside of the chamber is substantiallyequal to a flow rate of gas flowing out through the second gap from thefirst opening to an outside environment.
 2. A wafer processing apparatusaccording to claim 1, wherein a dimension of said first gap and aninside pressure of the chamber are defined such that the gas does notflow into an inside of the clean box through said first gap.
 3. A waferprocessing apparatus according to claim 1, wherein said door member isclosed, said first gap is maintained in gas fluidical communication withan inside and an outside of the chamber.
 4. A wafer processing apparatusaccording to claim 1, further comprising: one or more gas flow pathsformed at least at a vicinity of edges of said door, wherein said firstgap is in gas-fluidical communication with said one or more gas flowpaths, and wherein a flow rate of a gas flowing through the gas flowpath is substantially equal to a flow rate of the gas flowing from theinside of the chamber to the outside of the chamber through said firstopening when the door member is opened.
 5. A wafer processing apparatusaccording to claim 4, wherein the first gap is uniformly formed along aside of an outer peripheral shape of the door member.
 6. A waferprocessing apparatus according to claim 5, wherein the door member is insubstantially the shape of a square.
 7. A wafer processing apparatusaccording to claim 4, wherein the first gap is uniformly formed along aside of an outer peripheral shape of the lid when the lid is insertedthrough said first opening.